• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.397-402
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• 2003

The FM demodulation method for a bulk homodyne laser interferometer is presented. The Doppler frequency that represents the surface velocity of a vibrating object is obtained by using the bulk homodyne laser interferometer, and converted to the voltage signal by using the proposed analogue FM demodulation circuit. The DC offsets of the interferent signals that are obtained from the bulk homodyne interferometer are eliminated by using a simple subtraction. The new method for compensation of the asymmetry of each channels is presented. The light power variation of the interferometer is normalized by using the Auto Gain Controller(AGC). The proposed FM demodulation algorithm is proved by the theoretical method, and validated by the experimental results. In experiments, the proposed FM demodulation algorithm is compared with the conventional demodulation methods.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.208-211
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• 2005

The volumetric interferometer, which uses the interference of wavefronts emitted from two single mode fibers, measures the target position in 3-D. In this paper, we suggest a new calculation method which doesn't need a non-linear optimization and an initial guess. We find the relationship between the coefficients of the Zernike polynomials for a spherical wavefront and its center and reconstruct a spherical wavefront by using the Zernike polynomials from two interference fringes like a lateral shearing interferometer. The target position can be obtained from the coefficients of the Zernike polynomials of the reconstructed wavefront. We can get the target position in 3-D with $sub-{\mu}m$ errors in a simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.573-576
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• 2005

A compact linear and angular displacement measurement device was developed by combining a Michelson interferometer and an autocollimator to characterize the movement of a precision stage. A Michelson interferometer and an autocollimator are typical devices for measuring linear and angular displacement, respectively. By controlling the polarization of reflected beam from the target mirror of the interferometer, some part of light was retro-reflected to the light source and the reflected beam was used for angle measurement. The interferometer and the autocollimator use the same optic axis and the target mirror can be easily and precisely aligned orthogonal to the optic axis by monitoring the autocollimator s signal. The autocollimator was designed for angular resolution of 0.1 arcsec and dynamic range of 60 arcsec. The nonlinearity error of interferometer was minimized by trimming the gain and offset of the photodiode signals. Through the experiments, we evaluate the performance of measurement device and discuss its applications.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.63-71
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• 2005

When an almost flat surface under test is measured by an interferometer, the measurement result is largely influenced by systematic errors that include geometrical errors of a reference flat surface. To determine the systematic errors of the interferometer by the conventional method that is called the three flat method, we must take the reference flat surface out from the interferometer and measure it. Because of difficulties to set the reference flat surface to the interferometer exactly and quickly, this method is not practical. On the other hand, the method that measures a surface under test with some shifts in the direction being perpendicular to the optical axis of the interferometer is studied. However, the parasitic pitching, rolling and up-down movement caused by the above shifts brings serious error to the measurement result, and the algorithm by which the influences can be eliminated is not still established. In this paper, we propose the self-calibration algorithm for determining the systematic errors that include geometrical errors of a reference flat surface by several rotation shifts and a linear shift of general surface under test, and verify by a numerical experiment that this algorithm is useful for determining the systematic errors.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.310-312
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• 2009

The heterodyne laser interferometer has been widely used in precise measurement field. However, the accuracy is limited by the nonlinearity error caused from incomplete laser sources and nonideal optical components. In this paper, we propose the Dual-EKF which estimates states and weights simultaneously to improve the resolution of heterodyne laser interferometer. As a proof, we demonstrate the effectiveness of our proposed method through experimental results.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.269-273
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• 2004

The moduled interferometer with waveplates, polarizing beam splitter, etc. for four phase shifted interference patterns was stabilized with the and Fast Fourier Transform (FFT) method was used to investigate the surface profile measurement from the interferenece pattern from Twyman-Green interferometer using a mathcad.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.277-281
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• 2012

We measured small optical beam deflection in an image rotating Sagnac interferometer. We used a weak value measurement scheme that involves a pre-selection, weak perturbation, and a post-selection procedure to obtain the amplified value of beam deflection. The amplification factor of the measured beam deflection varied from 11 to 63 depending on the settings of the post-selection polarizer in front of the photodetector and the settings of polarization compensator in the interferometer.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.239-241
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• 2002

Basically, OCT used the interference effect of Michelson interferometer. First, we have analyzed the optical heterodyne interferometer for OCT. Second, we implement new optical heterodyne interferometer for OCT.

• Current Optics and Photonics
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• v.7 no.4
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• pp.325-336
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• 2023

We review recent research related to shearing interferometry, reported over the last two decades. Shearing interferometry is categorized as azimuthal, radial, or lateral shearing interferometers by its fundamental principle to generate interference. In this review the research trends for each technique are provided, with a summary of experimental results containing theoretical background, the optical configuration, analysis, and perspective on its application fields.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2001.11a
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• pp.119-122
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• 2001

We derived the resolution of the modified triangular interferometer and described the analysis about distance measurement using the one. Also, to demonstrate the feasibility of distance measurement using the modified triangular interferometer, the incoherent hologram of a two-point source with depth and its numerical reconstruction were presented.